1. Field of Invention
The present invention relates to switching power converter circuits employing secondary side regulation and, more particularly, to double ended switching power converters employing secondary side regulation circuitry to produce dual and/or interleaved outputs.
2. Related Art
FIGS. 1-4 are schematic diagrams showing power converter circuits employing secondary side regulation to produce two output voltages Vout1 and Vout2.
FIG. 1 employs a saturable reactor (mag amp) circuit including a transformer XFRMR (only the secondary winding being shown) coupled to two output regulation circuits. Each regulation circuit includes a series coupled saturable inductor L3, L4 connected from one end of the XRFMR to a shunt diode D1, D2, respectively. First transistors Qa, Qc are coupled in series with the saturable inductors L3, L4, respectively, with their drains terminating at nodes from which second transistors Qb, Qd are respectively connected in a shunt relationship to ground. Output filter inductors L1, L2 are coupled from the common nodes of Qa, Qb, and Qc, Qd, respectively, to filter capacitors C1 and C2. The regulated output voltages Vout1 and Vout2 are taken across filter capacitors C1 and C2, respectively.
A control circuit suitable for controlling diodes D1, D2 and transistors Qa, Qb, Qc, and Qd may be selected from any of the known circuits as would be readily apparent to one skilled in the art.
FIG. 2 shows a schematic diagram for another switching power converter circuit employing secondary side regulation. While the output filter configuration of the circuit shown in FIG. 2 is the same as that shown in FIG. 1, the arrangement of the regulation circuit elements differs. In particular, a single series diode D1 is employed instead of saturable inductors L3, L4 and shunt diodes D1 and D2. Further, transistors Qa and Qc are both coupled in series with diode D1 where the drains of transistors Qa and Qc are coupled together. The sources of transistors Qa and Qc are coupled to shunt transistors Qb and Qd, respectively. The regulated output voltages Vout1 and Vout2 are taken across output filter capacitors C1 and C2, respectively.
A control circuit suitable for providing control signals to transistors Qa, Qb, Qc and Qd may be selected from any of the known circuits as would be apparent to one skilled in the art in view of the above disclosure.
FIG. 3 shows a schematic diagram of yet another switching power converter circuit employing secondary side regulation. In that circuit, back-to-back transistors Qa1 and Qa2 are coupled in series between the XFRMR and the output filter inductor L1. Transistor Qb provides a shunt circuit from the back-to-back transistors to ground. Similarly, back-to-back transistors Qc1 and Qc2 are coupled in series between the XFRMR and the output filter inductor L2, with transistor Qd providing a shunt circuit to ground. The regulated output voltages Vout1 and Vout2 are taken across filter capacitors C1 and C2, respectively. A control circuit suitable for providing control signals to transistors Qa1, Qa2, Qb, Qc1, Qc2, and Qd may be selected from any of the known circuits as would be apparent to one skilled in the art having viewed the above disclosure.
FIG. 4 shows a schematic diagram of still another switching power converter circuit employing secondary side regulation. The circuit of FIG. 4 is substantially similar to the circuit of FIG. 3 except that back-to-back transistors Qa1 and Qa2 are replaced with an AC switch Qac1 and back-to-back transistors Qc1 and Qc2 are replaced with AC switch Qac2.
There is, however, a need in the art for a new circuit topology and control method to obtain secondary side regulation which results in improvements in cost and efficiency.
The present invention includes a switching power converter, comprising:
a secondary side transformer winding having first and second ends across which an AC voltage is inducible;
a first regulation circuit including: a first switching element having a power terminal coupled to the first end of the secondary side transformer winding and another power terminal coupled to a first intermediate node; a second switching element having a power terminal coupled to the first intermediate node and another power terminal coupled to a common node; and a first inductor coupled from the first intermediate node to a first output node;
a second regulation circuit including: a third switching element having a power terminal coupled to the second end of the secondary side transformer winding and another power terminal coupled to a second intermediate node; a fourth switching element having a power terminal coupled to the second intermediate node and another power terminal coupled to the common node; and a second inductor coupled from the second intermediate node to a second output node; and
a control circuit operable to deliver respective drive signals to respective control terminals of the first, second, third, and fourth switching elements such that the switching elements turn on and off in such a manner that first and second regulated voltages appear between the first and second output nodes and the common node, respectively.
Other objects, features, and advantages will be apparent to those skilled in the art from the disclosure herein.